1. Technical Field
This invention relates to surface winding and unwinding of cloth, paper, metal, or plastic webs and the like from web rolls. The present invention utilizes an equalizing roll to be used in manufacturing for providing equal tension across a web, belt, or sheet material during winding and conveying operations such as used in polymer film processing applications, corrugators, paper forming and cutting machines, printing presses, cloth winders and metal winding operations.
2. Background Information
The present invention comprises an equalizing roll which may be used as a stand alone unit or in a tracking apparatus for stabilizing the run of a material web which is being rolled off of or on to a drum, or through a series of rollers. The present invention is designed to provide a method of optimally stabilizing, controlling the tension, controlling the slack, and directing the web, belt, or sheet of material traveling between rolls.
One application is in the drying section of a high speed paper machine where the paper web to be dried meanders over drying cylinders. The equalizing roll of the present invention is also usable in connection with a “transfer foil”, i.e., a device for transferring the paper web from the press section to the drying section, such as described in U.S. Pat. No. 4,551,203 [Eskelinen]. The present invention may also be utilized for stabilizing and controlling the tension of a paper web of paper coaters. It is contemplated that the present invention can also be used in the fabric industry; plastics film, sheet, and tape industry; and in the metal film and foil industry. The invention may be used in small diameter, narrow width applications measurable in centimeters or inches or industrial operations wherein the rolls may extend thirty to fifty feet in length, or longer, depending upon the application.
The equalizing roll of the present invention in the paper industry solves the problem of wrinkles and slack being formed in the paper or plastic film web during processing by an apparatus such as described in U.S. Pat. No. 4,441,263 [Vendenpaa]. The present invention provides a means to control the pressure conditions in the area where the paper web runs together with a backing belt on a receiving drying cylinder and across the entire width of the paper web extending across the entire length of the drying cylinder or other such conveyor assembly. As is generally known, air flow transverse to the drying section causes the edges of the paper web to flutter and/or the formation of wrinkles in the paper web. This occasionally causes the paper web to break or a plastic web to be stretched and permanently distorted. A stable, smooth run of the paper web requires the forces resulting from longitudinal tension of the paper web to be equal. The longitudinal tension on the paper web caused by the drying cylinder in combination with a backing belt creates a region in the paper web where the curvature is irregular as viewed across the width of the paper web. In the center, the paper web bows out more heavily than on the edges resulting in stretching and deformation of the web.
Another application of the present invention is in the cloth industry to avoid wrinkling cloth being unwound from rolls or surface winders and unwinders, batchers, cradle let-offs, and the like, as described in U.S. Pat. No. 5,431,358 [Alexander], in the area where the support rolls engage the cloth roll, the cloth roll is indented presenting a shorter cloth roll radius at that point than the radius in the unengaged areas of the roll resulting in the formation of a bulge or bagging down in advance of the support roll. Sometimes the bulge or loose pucker resulting from such bagging down advances entirely about the wound roll causing wrinkling, marking and uneven tension.
Several patents including U.S. Pat. No. 1,738,130 [Cohen], U.S. Pat. No. 3,433,429 [Schnitzspahn] and U.S. Pat. No. 4,026,487 [Ales] describe various efforts made over the years to solve the problem through compressible support roll coverings to match the compressibility of the support or; to the compressibility of the wound web roll. An inflatable support roll and other efforts to solve the problem include uniform or continuously spaced fluting on the support rolls. Such fluting may be skewed or spiraled in respect to the longitudinal axis. A roll having spaced segments is described in U.S. Pat. No. 1,093,913 [Church]. Conversely, U.S. Pat. No. 3,239,163 [Cmiglio] describes uniformly spaced compressible fluting having upper surface areas conforming to the curvature of the flexible roll. Attempts to match or otherwise utilize the relative compressibility of the support rolls in relation to the compressibility of the wound rolls have met with limited success. Fluted rolls having uniform circumferential spacing cause vibration or chattering, and sometimes mark the wound rolls with the pattern of the fluted segments due to the limited areas of support.
The present invention provides an equalizing roll means to equalize the tension of the web as the web material runs over the rolls distributing the lateral forces so that any imbalance of lateral tension will cause the roll to pivot at its center permitting the roll to move forward on the side of least tension until the web tension is equalized across the entire roll.